Forced flow steam generating system



April 14, 1959 A. BURI I 2,881,741

FORCED FLOW STEAM GENERATING SYSTEM Filed Dec. 20. 1954 2 SheetsSheet 11 INVENTOR.

A LFRED BUEI.

BYKXIW- A. BURI FORCED FLOW STEAM GENERATING SYSTEM April 14, 1959 2Sheets$heet Filed Dec. 20. 1954 INVENTUR.

/] LFRED BU/Pl.

FORCED FLOW STEAM GENERATHQG SYSTEM Alfred Buri, Winterthur,Switzerland, assignor to Snlzer Freres, Societe Anonyme, Winterthur,Switzerland, a corporation of Switzerland Application December 20, 1954,Serial No. 476,188

Claims priority, application Switzerland December 24, 1953 6 Claims.(Cl. 122-.-33

The present invention relates to a forced flow vapor generator providedwith a conduit for diverting operating medium from the tube system ofthe vapor generator and a heat exchanger interposed in theaforementioned conduit for transferring heat from the diverted operatingmedium to the liquid operating medium flowing through the vaporgenerator. The system according to the invention is characterized by aflow control means for the operating medium in the aforementionedconduit downstream of the heat exchanger. This flow control means may beactuated in accordance with the pressure of the diverted operatingmedium while it flows through the heat exchanger. Alternatively, theflow control means may be actuated in accordance with the temperature ofthe operating medium at a suitable point in the tube system or at theoutlet of the vapor generator.

The term vapor used in the present application includes steam. Where theword steam is used, this includes vapor of substances other than water,The term water used in the present specification includes any otheroperating medium in liquid state.

It has been proposed to divert operating medium from the tube system ofa forced flow vapor generator for controlling the temperature of thesuperheated vapor leaving the vapor generator and to use the divertedoperating medium for heating operating medium flowing in liquid state toor through the tube system of the gen.- erator. For this purpose aconduit is connected to the tube system of the vapor generator forconducting heating vapor through the primary side of a heat exchanger inwhich the heat content of the diverted operating medium is transferredto operating medium for the vapor generator in liquid state, and forreturning the divertedop crating medium after it has given upv heat tothe liquid operating medium, to the circuit of the operating medium ofwhich the vapor generator forms a part. The flow of operatingmediumthrough the aforementioned conduit is controlled by atemperature-actuated valve disposed in the first part of the conduit.Since the diverted operating medium usually has a higher temperaturethan the temperature of bleeder steam which is used for feed waterpreheating in conventional steam turbine plants, the heat exchangerwhich is heated by operating medium diverted from the tube system of thevapor generator is preferably arranged downstream, with respect to thedirection of flow of the feed water, of the last feed. water heaterwhich is heated by bleeder steam, so that advantage can be taken of thehigh temperature of the diverted operating medium without impairing theefliciency of the feed water heating system which receives heat frombleeder steam.

If the conduit receiving the diverted operating medium nited StatesPatent from the heat exchanger after the medium has released 2,881,741Patented Apr. 14, 1959 of the vapor generator. The pressure in theprimary side of the heat exchanger is approximately the same as thepressure in the feed water reservoir. A temperature, is coordinated tothis pressure at which the operating me.- dium condenses. If thetemperature of the liquid operatingmedium in the feed water reservoir ishigher than the aforementioned condensation temperature, the divertedoperating medium does not condense, but flows in vapor state, withoutreleasing heat of condensation, through the feed water reservoir and isblown into the condenser, if the pressure in the reservoir becomes toogreat. In this case, the heat content of the diverted operating mediumis carried away by the condenser coolant and is wasted;

If a steam trap is interposed in the conduit for the diverted operatingmedium downstream of the heat exchanger, the pressure in the heatexchanger can 'be maintained sufiiciently high, but only the condensateis re;- moved, independently of the position of the valve at the inletof the conduit for the diverted operating medium. This makes asatisfactory control impossible. If the pressure at the primary side ofthe heat exchanger is above the critical pressure, a steam trap isineffective, because vapor and liquid have approximately the samedensity, and no liquid level can develop in the steam trap.

In contradistinction to the aforedescribed conventional arrangements,the system according to the inventioncornprises a flow control meanswhich is interposed in the conduit receiving operating medium from theheat exchanger after it has given up heat therein. This. arrange mentaffords maintenance of a sufliciently high pressure in the heatexchanger as well as diversion of an amount of' operating medium whichaffords a satisfactory control of the temperature of the operatingmedium leaving the vapor generator. The flow control means may beactuated in accordance with the pressure in the heat exchanger. Forexample, a predetermined pressure may be maintained in the heatexchanger. If the pressure rises, for example because thetemperature-controlled valve at the inlet of the conduit for divertingoperating medium opens wider, the flow control means downstream of theheat exchanger will also open wider, and either condensed or vaporizedoperating medium will be blown off. It is also possible to arrange atemperature-controlled valve at a point downstream of the heatexchanger, instead of at the beginning of the conduit for the divertedoperating medium. In this case also, the pressure reduction willessentially occur downstream of the heat exchanger, so that asufliciently high pressure. and correspondingly high condensationtemperature prevail in the heat exchanger.

The, novel features which are considered characteristic of the inventionare set forth with particularity in. the appended claims. The inventionitself however and additional objects and advantages thereof will bestbe understood from the following description of embodiments thereof whenread in conjunction with the accompanying drawing, in which Fig. l is adiagram of a steam power plant according to the invention;

Fig. 2 is a diagram of a modified part of the steam power plantillustrated in Fig. l.

The same numerals designate the same parts in both figures.

A condensate pump 2 draws condensate from a condenser 1, and forces itthrough a conduit 3 into a reservoir- 4 for liquid operating medium ofthe plant. A feed pump 5 pumps liquid operating medium from thereservoir 4 through a conduit 6 into a tube system including a primaryheating surface 7 of a vapor generator 25. The operating medium which ispreliminarily heated in the flue gas-heated heater or economizer 7 flowsinto the secondary or heat receiving side of a heat exchanger 8,

and therefrom into a second heating section 9 disposed in the combustiongas flow of the generator 25. The liquid operating medium is convertedinto vapor in the heating section 9, the vapor being conducted through aconduit 10 into a third combustion gas-heated heating section orsuperheater 11. The superheated operating medium flows through outletmeans of the tube system into a main 12.and into a turbine 13 whichdrives an electric generator 14. The exhaust of the turbine 13 isconducted through a conduit 15 into the condenser 1.

For controlling the operation of the plant, a minor portion of theoperating medium is diverted from the conduit 10 by means of a conduit16 in which a flow control means or valve 18 is inserted. In themodification shown in Fig. l, the valve 18 is actuated by means of adevice 17 which is responsive to the temperature of the operating mediumin the main conduit 12. The valve '18 is opened when the temperature inthe steam main 12 falls, and vice versa. Downstream of the valve 18, theprimary side of the heat exchanger 8 is interposed in the conduit 16 forreceiving heating fluid from the conduit 16. After the operating mediumsupplied through the conduit 16 to the heat exchanger 8 has been cooledby releasing heat to the operating medium flowing from the heatingsection 7 of the vapor generator to the heating section 9 of thegenerator, the operating medium flows through a valve 19 into thereservoir 4. The valve 19 is actuated by means of a device 20 which isresponsive to the pressure of the operating medium upstream of the valve19, which is the pressure prevailing in the primary side of the heatexchanger 8. The valve 19 is opened when the pressure in the primaryside of the heat exchanger rises, and vice versa.

In the modification illustrated in Fig. 2, the temperature-controlledvalve 18 in the conduit 16 upstream of the heat exchanger 8 is omitted,and the valve 19, which is designated by numeral 21 in Fig. 2, isactuated by the device 17 which is responsive to the temperature of theoperating medium in the main conduit 12. The valve 21 is opened when thetemperature in the steam main falls, and vice versa. Since the pressureof the operating medium upstream of the valve 21 and consequently alsoin the primary side of the heat exchanger 8 is approximately the same asthe pressure of the operating medium in the vapor generator, thegreatest possible amount of heating vapor is condensed in the heatexchanger 8, the condensate flowing through the valve 21 into thereservoir 4. At sufficiently wide opening of the valve 21, a part of theoperating medium will not be condensed in the heat exchanger 8- and willarrive in the reservoir 4 in vapor state. If the pressure in thereservoir 4 becomes too great, vapor need not be blown ofI' into theatmosphere, but is conducted through a conduit 22 into the condenser 1.The flow of vapor through the conduit 22 is controlled by'means of avalve 23 which is actuated by a device 24 which is responsive toexcessive pressures in the reservoir 4.

Many variations of the illustrated system may be made without departingfrom the scope of the present invention. The secondary side of the heatexchanger 8 may be arranged upstream instead of downstream of the heateror economizer 7. The temperature-responsive flow control means 18 may bearranged at a point of the tube system difierent from the oneillustrated. The drawing is a diagrammatic showing only. An actual plantwill have a great number of additional valves arranged in theconventional manner and will probably have conventional bleeder.steam-heated preheaters for the liquid operating 1 medium. The heatingsurfaces for the operating medium and/or the turbine 13 may besubdivided in various conventional ways.

What is claimed is: 1. A vapor generating system comprising a forcedflow vapor generator including a vapor generating tube system, outletmeans from said vapor generating tube system adapted to conduct vapor toa consumer, a source of supply of relatively cold operating medium, apump interposed between said source of supply and said tube system forpumping operating medium from said source into and through said tubesystem to said outlet means, an indirect heat exchanger having asecondary or heat receiving side interposed in said tube system for flowof operating medium through said heat exchanger, a first conduitconnected with a relatively hot portion of said tube system downstreamof said heat exchanger and upstream of said outlet means, said firstconduit being connected with the primary or heat delivery side of saidheat exchanger for diverting a minor portion of the operating mediumflowing through said tube system as a heating medium into said heatexchanger, a second conduit connecting the primary side of said heatexchanger with said source for returning the diverted operating mediumto said source, and a flow control means interposed in said secondconduit for maintaining the pressure of the operating medium in theprimary side of said heat exchanger above the pressure of the operatingmedium in said source.

2. A vapor generating system as defined in claim 1 in which said tubesystem includes an evaporating section and a superheating section and inwhich said first conduit is connected with said tube system between saidevaporating section and said superheating section.

3. A vapor generating system as defined in claim 1 in which said tubesystem includes an economizer section and an evaporating section and inwhich said secondary side of said heat exchanger is interposed foroperating medium flow between said economizer section and saidevaporating section.

4. A vapor generating system as defined in claim 1, including anactuating device connected with and responsive to the pressure of theoperating medium in the primary side of said heat exchanger and beingconnected with said flow control means for opening the latter when thepressure of the operating medium in the primary side of said heatexchanger rises, and vice versa.

5. A vapor generating. system according to claim 4, including a flowcontrol means interposed in said first conduit, and an actuating meansconnected with and responsive to the temperature of the operating mediumleaving said tube system and being connected with said flow controlmeans which is interposed in said first conduit for opening said lastmentioned flow control means when the temperature of the operatingmedium leaving said tube system falls, and vice versa.

6 A vapor generating system as defined in claim 1, including anactuating device connected with and responsive to the temperature of theoperating medium leaving said tube system and being connected with saidflow control means for opening the latter when the temperature of theoperating medium leaving said tube system falls, and vice versa.

References Cited in the file of this patent UNITED STATES PATENTS

